1. Technical Field
Aspects of the present invention relate to a printer for executing inkjet printing on fabric held by a fabric holding frame.
2. Description of Related Art
A variety of printing techniques have been proposed for printing desired patterns, designs, etc. on various types of fabrics, and a variety of inkjet printing devices, capable of printing desired patterns, designs, etc. on the surface of fabric by moving the fabric or a print head relative to each other in an X direction and a Y direction (orthogonal to the X direction) while letting ink nozzles discharge color ink onto the fabric according to print data, have been proposed.
For example, in a printer described in Japanese Patent Provisional Publication No. HEI 05-84887 (hereinafter referred to as '887 publication), an X-movement bar is held to be movable in a direction along grooves formed on both lateral faces of a machine frame which is formed in a U-shape in the plan view, an X-movement arm is supported by the X-movement bar to be movable along the X-movement bar, a printing unit is attached to the end of the X-movement arm, and a fabric holding frame holding fabric to be printed on is mounted on a table which is placed at the center of the machine frame. In the printer, the distance between the top of the machine frame and an attaching portion attaching the fabric holding frame to the machine frame (fabric thickness) is detected by a fabric thickness sensor provided at the top of the machine frame, and the height of the table is changed, using a motor, depending on the detected fabric thickness.
In the printing unit of the printer, a plurality of ink heads are supported by a head supporting member to face downward, and the height of the head supporting member is changed by a head motor while detecting the height of the ink heads from (relative to) the surface of the fabric by use of a noncontact optical sensor placed in the vicinity of the ink heads. When the printing is started, the height of the ink heads is set to be a prescribed height higher than the surface of the fabric based on the fabric thickness detected by the fabric thickness sensor. Meanwhile, when the detected fabric thickness changes due to small pieces of fabric (applique, etc.) sewn on the fabric, the height of the ink heads is changed by activating the head motor so as to keep a constant height of the ink heads from the surface of the fabric.
In the printer disclosed in the '887 publication, the printing unit is provided with the noncontact optical sensor placed in the vicinity of the ink heads in order to detect the height of the ink heads from the surface of the fabric (i.e. head gap). In this configuration, ink mist discharged from the ink heads during printing adheres to the noncontact optical sensor and when a photoreceptor unit or a photoemitter unit is smeared with the ink mist, the distance to the surface of the fabric can not be detected precisely and the head gap can not be set correctly.
Also when the fabric has frayed parts, fuzzy parts, lint, embroidery, etc. thereon, the distance to the surface of the fabric can not be detected precisely and the head gap can not be set correctly. Further, the head gap can not be set correctly also when reflecting conditions (e.g. reflectance) of light emitted by the photoemitter unit vary depending on the material or color of the fabric.